Topic 1: Cells
Cell Theory
Discuss the theory that living
organisms are composed of cells.
 The Cell Theory states that:

– All organisms are composed of one or more
cells.
– All cells arise from pre-existing cells.
– All vital functions of an organism occur
within cells.
– Cells are the most basic unit of life.
– Cells contain hereditary information. Why?
Evidence for Cell Theory
What is Evidence?
 What is a theory?
 Evidence for Cell theory:

– Living tissues= composed of cells
– Cells of an organism can sometimes survive on
their own but smaller cell components can
NOT.
– Classic experiments showed that spontaneous
generation of life= impossible.
Exceptions to aspects of the
theory?
 Skeletal muscle –
multinucleate cytoplasm
 Some fungal hyphaemultinucleate cytoplasm.
 Extracellular material
(material outside the cell
membrane), such as teeth
and bone, forms a
significant part of the body.
 Some biologists consider
unicellular organisms to be
acellular.
Do you think these constitute
exceptions to cell theory?
Justify your answer.

State that unicellular organisms
carry out all the functions of life.
 Discussion: What are the necessary
functions of life?

Metabolism
 Response to stimuli
 Homeostasis
 Growth/development
 Reproduction
 Nutrition
 Excretion of wastes


HW:Research each function of life in a Paramecium and
Euglena. Create a Data Table for comparison.








Compare the relative sizes of molecules, cell
membrane thickness, viruses, bacteria,
organelles and cells, using appropriate SI
units.
Molecules (1 nm) (Smallest)
Cell membrane thickness (10 nm)
Viruses (100 nm)
Bacteria (1 µm)
Organelles (<10 µm)
Most cells (<100 µm) (Largest)
Interactive
http://www.cellsalive.com/howbig.htm
 Calculate
linear
magnification of
drawings.
– Drawings should
show cells and cell
ultrastructure.
 Include:
– A scale bar: |------| =
1 µm
– Magnification: ×250
 To
calculate
magnification:
– Magnification =
Measured Size of
Diagram ÷ Actual Size
of Object

Explain the importance
of the surface area to
volume ratio as a
factor limiting cell size.
– The rate of
exchange of
materials
(nutrients/waste)
and energy (heat) is
a function of its
surface area.
(Why?)
– As cell size
increases, the
surface area to
volume ratio
decreases
 This can make
the exchange
rate inadequate
for large cells
– Cell size, therefore,
remains small

Explain that cells in
multicellular
organisms
differentiate to
carry out
specialized
functions by
expressing some of
their genes but not
others.
– Differentiation:
becoming specialized
in structure and
function.
– Supporting examples?
– Multicellular organisms
show emergent
properties (What??)

See ex. Next slide…
Video: http://www.pbs.org/wgbh/nova/sciencenow/archive/title-m-z.html




Define tissue, organ
and organ system.
Tissue: An integrated
group of cells that
share stucture and are
adapted to perform a
similar function.
Organ: A combination
of two or more tissues
which function as an
integrated unit,
performing one or more
specific functions.
Organ system: A
group of organs that
specialize in a certain
function together.


STEM CELLS
Stem cells
– Retain the capacity to divide
– Have the ability to differentiate
along different pathways.
Therapeutic Use:
– Many possibilities
 Repair of damaged tissue
– Actual uses
 Restore neural insulation
tissue in rats.
 Use of umbilical cord blood
stem cells for leukemia
patients.
– Sources and ethical issues:
 Embryonic
 placenta/umbilical cord
 Many other tissues have
stem cells
 Pluripotent vs.
totipotent/omnipotent Video: http://www.pbs.org/wgbh/nova/sciencenow/archive/title-m-z.html
Stem Cell Uses

Stargardt’s Disease– Macular (eye) degeneration, causes
central vision loss while periphial vision is
still retained
– Photreceptors in the retina deteriorate.
–


https://www.google.com/search?q=stargardt's+disease&source=lnms&tbm=isch&sa=X&ei=hTLxU8O2DI2JogTA9oLIDA
&sqi=2&ved=0CAYQ_AUoAQ&biw=1366&bih=565
Stem cell treatment
– using embryonic stem cells to grow new
retina cells containing new photoreceptors.
– These stem cells are transplanted into the
patients retina to restore vision.
HW: Research another Stem Cell Treatment and record into
your notebook
Prokaryotic Cells


Draw a generalized
prokaryotic cell as seen in
electron micrographs
The diagram should include:
– the cell wall,
– plasma membrane,
– cytoplasm,
– Pili
– Flagella
– Ribosomes
– nucleoid ( region
containing naked DNA).







State one function for each
of the following: cell wall,
plasma membrane,
mesosome, cytoplasm,
ribosomes and naked DNA.
Cell Wall: Maintains the cell's
shape and give protection.
Plasma Membrane: Regulates
the flow of materials
(nutrients, waste, oxygen,
etc.) into and out of the cell.
Mesosome: A tightly folded
region of cell membrane.
(has attached proteins for
respiration/photosynthesis)
Cytoplasm: Holds and
suspends the cell's
ribosomes and enzymes.
Ribosome: Protein synthesis.
Nucleoid region: Contains the
cell's genetic material (naked
DNA)
Binary Fission

Prokaryotic cells
divide by binary
fission
– Asexual
– splits directly into
two equal-sized
offspring, each with
a copy of the
parent's genetic
material.
Identify parts of a Prokaryote
Using an Electron Micrograph
Harvard Animation
 Why
are cells cool?
 http://multimedia.mcb.harvard.edu/
Eukaryotic Cells
Draw a diagram
to show the
ultrastructure
of a
generalized
animal cell
(liver cell) as
seen in
electron
micrographs.
 Should include
free ribosomes,
rough and
smooth ER,
lysosome, Golgi
apparatus,
mitochondria,
and nucleus.
An Animal Cell
Liver cell electron micrographs (objective 1.2)

1.
2.
3.
4.
5.
Nucleus
Mitochondria
Cell border
Nucleoli
Red blood cell



Define organelle.
An organelle is a discrete
structure within a cell, and has
a specific function.
Describe the functions of the
following organelles: (see p.
114/ch.7 of Campbell…)
– mitochondrion
– golgi body
– endoplasmic reticulum
– vacuole
– lysosome
– ribosome In contrast to the
other organelles, they are
not surrounded by a
membrane.
– centriole (Unique to animal
cells)
– chloroplast
EUKARYOTE CELL ULTRASTRUCTURE
Practice: What are
the respective
magnifications of the
cell as a whole and of
each of its organelles
in the following cell
picture?
Summary of the major cell organelles:
ORGANELLE
MAIN
FUNCTIONS
DIMENSIONS
Nucleus
Cell division,
protein
synthesis
10 µm diameter
Mitochondrion
Respiration
pathways
Chloroplast
Photosynthetic
pathways
Lysosome
Digestion,
recycling &
isolation
Golgi apparatus
Secretion,
reprocessing,
lysosome
synthesis
Cisternae:
0.5µm thick, l3µm diameter
Endoplasmic
Reticulum (ER)
Support, Golgi
apparatus
synthesis.
26 to 56 nm
thick
Ribosome
Protein
synthesis
1.0 to 12.5 µm
5 to 10 µm
diameter
0.5 to 3.0 µm
diameter
20 nm diameter
State one function of each of
these organelles: ribosomes,
rough endoplasmic reticulum,
lysosome, Golgi apparatus,
mitochondrion and nucleus.






Ribosomes: protein synthesis
Rough endoplasmic reticulum
(rER): Packages proteins
Lysosome: digests old cell
parts, macromolecules (food)
and engulfed viruses/bacteria
Golgi apparatus: Modifies,
stores and routes products of
the endoplasmic reticulum.
Mitochondrion: cellular
respiration.
Nucleus: contains genetic
material
Prokaryotic cells vs. Eukaryotic cells
 Contain naked DNA vs. DNA associated with
protein
DNA in cytoplasm vs. DNA enclosed in a nuclear
envelope
 No membrane-enclosed organelles vs.
membrane-enclosed organelles (e.g.,
mitochondria, chloroplasts)
 70S vs. 80S ribosomes


Describe three differences between plant
and animal cells.





Only plant cells have:
Cell walls
Chloroplasts
Large central vacuoles and
tonoplast
Plasmodesmata
Starch granules for storage of
carbohydrates
Only animal cells have:
Centrioles
Lysosomes
Glycogen for storage of carbohydrate
Also: Plant cells usually have much
less cholesterol in their plasma
membranes.
Roles of extracellular components
(2.3.6)
 Animal
cells
– Extracellular matrix (secreted
glycoproteins)
 Support
 Adhesion
 Movement
 Plant
cell wall (see next slides)
Structure and function of organelles within
exocrine gland cells of the pancreas and within
palisade mesophyll cells (1.2)
and within palisade mesophyll
cells (1.2)
Plant cell wall

Main component= cellulose
– Cellulose molecules are arranged in bundles called
microfibrils.
 give the cell wall great tensile strength and allow high
pressures to develop inside the cell.
 Functions= structure, support, protection.



Draw a diagram
of the fluid
mosaic model.
http://www.youtu
be.com/watch?v=
Qqsf_UJcfBc
Diagram should
show
– the
phospholipid
bilayer,
– cholesterol,
– glycoproteins,
– Integral proteins
– peripheral
proteins.
Membranes
Explain how the hydrophobic and
hydrophilic properties of
phospholipids help to maintain the
structure of cell membranes.
Hydrophilic
-”water loving”
-phosphate heads
Hydrophobic
-”water-fearing”
-fatty acid tails
Functions of membrane proteins
Hormone binding sites.
 Enzymes
 Cell adhesion

– Attachment to the cytoskeleton and
extracellular matrix

Cell communication
– Signal transduction
– Cell-cell recognition
Channels for passive transport
 Pumps for active transport.
 Electron carriers

Define diffusion

Diffusion: the
passive
movement of
particles from a
region of higher
concentration to
a region of lower
concentration,
as a result of the
random motion
Animation
of particles.
http://www.indiana.edu/~phys215/lecture/lecn
es/lecgraphics/diffusion2.gif
Define Osmosis
Osmosis: the passive movement of
water molecules, across a
selectively permeable membrane,
from a region of lower solute
concentration to a region of higher
solute concentration. (i.e. the
diffusion of water)
Remember: Lowers solute
concentration = higher water
concentration!!!
Hypertonic (hyperosmotic)
Hypotonic (hypoosmotic)
Isotonic (isoosmotic)
http://www.tvdsb.on.ca/westmin/sci
ence/sbi3a1/Cells/Osmosis.htm
effect of osmosis on cell animation
Explain passive transport across membranes in terms
of diffusion.
 Simple
diffusion
 facilitated diffusion.
– No ATP used
– Channel proteins (integral membrane
proteins)
– Down concentration/electrochemical
gradient
– Specific

ex. Ion Channels in neurons
Explain the role of protein pumps and ATP in
active transport across membranes.

Active transport is the
movement of substances
across membranes using
energy from ATP.
– moves substances against a
concentration gradient.

Active transport
animations:http://www.bbc.co.uk
Carrier proteins– protein
pumps
Types of transport






Explain how vesicles are
used to transport
materials within a cell
between the rough
endoplasmic reticulum,
Golgi apparatus, and
plasma membrane.
Proteins synthesized by
ribosomes
enter the rough
endoplasmic reticulum.
Vesicles bud from rER and
carry the proteins to the
Golgi apparatus.
Golgi apparatus modifies
the proteins.
Vesicles bud off from the
Golgi apparatus and carry
the modified proteins to
the plasma membrane.
Describe how the fluidity of the membrane allows it to
change shape, break and reform during exocytosis.
In exocytosis vesicles fuse with the plasma membrane.
The contents of the vesicles are then expelled. The
membrane flattens out again.
animations:http://www.bbc.co.uk/education/asguru/biolo


In
Describe how the fluidity of the membrane
allows it to change shape, break and reform
during endocytosis
endocytosis part of
the plasma membrane
is pulled inwards.
A droplet of fluid
becomes enclosed
when a vesicle is
pinched off.
Vesicle can then
move through the
cytoplasm carrying its
contents.
Cell Division





State that mitosis is
division of the nucleus
into two genetically
identical daughter nuclei.
New cells are produced by
the division of existing cell,
remember the cell theory.
Interphase: DNA replication
and transcription occurs.
Also, normal cell life.
Mitosis: Cell begins to
divide.
Cytokinesis: The cell finishes
dividing and the cytoplasm
splits between them.
Mitosis
 http://highered.mheducation.com/ol
cweb/cgi/pluginpop.cgi?it=swf::535:
:535::/sites/dl/free/0072437316/12
0073/bio14.swf::Mitosis%20and%20
Cytokinesis


Beginning of Cell Cycle
Interphase is an active period in the life of a cell
when many biochemical reactions occur:
– protein synthesis (transcription and translation)
– DNA Replication
– Increase in number of mitochondria and/or
chloroplasts etc.
Interphase continued…

Phases of Interphase
– G1 = growth,
protein synthesis,
increase
mitochondria/
chloroplasts
– S = DNA
Replication
– G2 = growth,
increase in
organelles,
preparation for cell
division.
What controls Cell Cycle?


Cyclins
– Control Cell Cycle
– Proteins that ensure that tasks within the Cell Cycle are
performed at the correct time and moves the cell on to the next
stage of the cycle when appropriate
– Four groups of Cyclins (1 per stage)
How do they do it?
– Cyclins bind to enzymes called cyclin-dependent kinases
 These kinases become active and attach phosphate groups
to other proteins which triggers a reaction that carries out
tasks specific to one of the phases of the cell cycle
– Unless these cyclins reach a threshold concentration, the cell
does not progress to the next phase in the cell cycle.
Describe the events that occur in the four
phases of mitosis…
Prophase


the mitotic spindle (made
from microtubules) starts
growing (going from pole to
pole).
Condensation of
Chromosomes
– Chromatin coils up to form
distinct chromosomes.
– Process is called Supercoiling
(Each chromosome contains two
identical sister chromatids,
attached to each other at the
centromere region.)

The nuclear envelope starts
breaks down.
…Describe the events that occur in the
four phases of mitosis…




each chromosome
attaches to two spindle
microtubules (one going
to each pole) at the
centromere.
line up at the equator
mitotic spindle is fully
developed
some microtubules are
attached to
chromosomes and reach
to the equator; others go
from pole to pole.
…Describe the events that occur in the
four phases of mitosis…

Anaphase
– the spindle
microtubules
pull the sister
chromatids to
opposite poles
– each sister
chromatid
becomes one
new
chromosome
of the daughter
cell.

Telophase
– each sister chromatid reaches its pole (becoming a
chromosome).
– nuclear envelope starts to reform. Spindle microtubles
deteriorate.
Cytokinesis (division of the cytoplasm) takes place.
Summary of
Mitosis
Summary of mitosis continued
In your journal
 Explain
how mitosis produces
two genetically identical nuclei.
(an IB standard)

Outline the differences in
mitosis and cytokinesis
between animal and plant
cells.
(limit this to the lack of the
centrioles in plant cells and the
formation of the cell wall.)


Animals:
– Centrioles
– No cell wall
Plants:
– No centrioles
– Cell wall (cell plate) is
formed between cells as
vesicles transport cell wall
materials to middle.





State that mutagens,
oncogenes and
metastasis are involved
in the development of
primary and secondary
tumors.
Cancer cells do not respond
to cell cycle regulation
Mutagens– Agents that
produce changes in genes
involved in controlling the
cell cycle
– Produce Oncogenes that
cause uncontrolled Cell
Division
Tumor: benign (don’t
spread) or malignant (do
spread)
– Result from uncontrolled
cell division
Metastasis – spreading of
cancer cells to other areas
Cancer
 http://www.pbs.org/wgbh/nova/canc
er/ (Cancer Warrior– angiogenesis
resources)
http://www.pbs.org/wgbh/
nova/cancer/program.html
(Video: Cancer Warrior-angiogenesis)
 http://www.pbs.org/wgbh/nova/canc
er/grows.html


State that a virus is
a non-cellular
structure consisting
of DNA or RNA
surrounded by a
protein coat.
Characteristics of
Viruses
– not considered living
– no metabolism.
– Unable to reproduce
without a host
– Others?

Explain three
advantages of
using light
microscopes.
– color instead of
monochrome (black
and white) images.
– large field of view.
– Facilitate preparation
of sample material.
– Allow for the
examination of living
material and the
observation of
movement.
– Relatively
inexpensive

Outline the advantages of using
electron microscopes.
1) higher resolution and magnification than light microscopes.
– Resolution refers to the ability to distinguish two objects
as seperate entities.
– Magnification refers to the ability to increase the size of
a viewed object.
2) May provide a three dimensional view.
 Scanning Electron Microscopes (SEM) provide images of the
specimen's surface
 Transmission Electron Microscopes (TEM) provide images of
a sample's interior. The resolution of an SEM is
approximately half that of a TEM.
TEM
SEM